Variable ratio rotary pump and motor hydraulic transmission



July 21, 1953 D. A. ELKlNs VARIABLE RATIo, ROTARY PUMP AND MoToRHYDRAULIC TRANSMISSION 8 Sheets-Sheet l Filed Feb. 20, 1947 8Sheets-Sheet 2 D. A. ELKINS VARIABLE RATIO, ROTARY PUMP AND MOTORHYDRAULIC TRANSMISSION NWI] July 2l, 1953 Filed Feb. 20, 1947 M ."L v

R aF-Q IN V EN TORI DOUGLAS A. ELK/NS,

LKlNS ROTARY P July 2l, 1953 D. A. E VARIABLE RATIO, UM K MOTORHYDRAULIC TRANSMISSI Filed Feb. 20, 1947 8 SheebS-S'hee'tI 3 INVENTOR:DOUGLAS A. ELK/NS,

July 21, 1953 D. A. ELKlNs 2,645,903

VARIABLE RATIO, ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION Filed Feb.20, 1947 8 Sheets-Sheet 4 DOUGLAS A. ELK/Mg July 21, 1953 D. A. ELKlNsVARIABLE'RATIO, ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION 8Sheets-Sheet 5 Filed Feb. 20, 1947 INVENTOR.' UGLS ELK/M5, BY

July 2l, 1953 D. A. ELKlNs 2,645,903

VARIABLE RATIO,l ROTARY PUMP AND uoToR HYDRAULIC TRANSMISSION med Feb.2o. 1947 a sheets-sheet e INVENTOR.' DUGLS A. ELK/N- @au a 54 63assoir/6062 sa July 21, 1953 n. A. ELKlNs 2,645,903 VARIABLE RATIO,ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION mea Feb. 2o. 1947 8Sheets-Sheet 7 ,7 ,8 my. Je.

a l v V INVENTOR. DOUGLAS A. ELK/N5, BY' d July 21, 1953 D. A. ELKlNs2,645,903

` VARIABLE RATIO, ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION 8Sheets-Sheet 8 Filed Feb. 20. 1947 TQM.

v INVENTOR: 1 6 S A. ELK/N3,

Patented July 21.,r 195:3

VARIABLE RATIO ROTARY `PUMP AND MOTOR HYDRAULIC TRANSMISSION Douglas A.Elkins, Salt Lake City, `Utah Application February 20, 1947, Serial No.729,731

20 Claims. (Cl. 60-53) This invention relates to power transmissions,and particularly to' innitely variable power transmissions of hydraulictype.

Power transmissions are employed as agencies for transmitting rotativemotion from a primary power source to a power output at selectivetransmission ratios, that is to say, at selectively different ratios ofinput torque to output torque, or,

to express it differently, at selectively diierent ratios of input speedto output speed. A major eld of use for such devices is in the art ofpowered propulsion, where an engine or motor is utilized to drive avehicle or the like at various drive ratios selectively determined inaccordance with the needs of the moment. The selection of a particulardrive ratio may be made manually by the operator of the vehicle, as inthe case of the usual hand-manipulated gear shift of conventionalautomotive transmissions, or may be made automatically, as is done byVarious known types of automatically controlled transmissions.

The number of possible drive ratios available in a given mechanism maybe rigidly xed by the construction of the transmission, as is true ofthe conventional three forward gear ratios orf being low at low speeds,increasing to a maximum at an intermediate speed, and dropping off againat top speeds.

2. For any given engine speed, the fuel consumption per horsepower houris lowest at maximum load or torque, and mounts rapidly as the per centof maximum load is decreased.

3. Lowest specific fuel consumption is obtained at an intermediateenginespeed.

When an automobile is driven at axed gear ratio under varying drivingconditions, the following disadvantageous condition necessarily exists:At normal driving speeds there must beysome excess engine torqueavailable to prevent sluggishness of operation. That is, there must besome reserve torque available at such `engine speeds in order tobe abletoaccelerate the car lof operation ,is quite considerable.

r,quickly from rthose speeds to higher speeds, or

to care rforrvariations in resistance caused vby kshifting winds andirregularities in road grade. The excess torque made available inmodern, high powered automobiles under average conditions This meansthat in average ,operation the engine is operating low on its torquecurve, which in turn means operation at low economy.

The infinitely variable power transmission of this invention makes itpossible for the engine to operate high on its 'torque curve in order toobtain maximum economy, without sacrificing the flexibility ordinarilyobtained by having considerable excess torque available.

The Vpresent disclosure does not deal specically with operationalcontrols required rfor installation along with the transmission of theinvention in an automobile, butdoes cover the vtransmission itself in aform admirably suited to automotive installations; and, while thetransmission ofthe invention is especially applicable to automotive use,it may be employed generally in a wide variety of forms, either manuallyvariable or automatically variable, designed for the particular need.

The transmission of the invention is of hydraulic type, and in all formsthereof includes two mutually independent power shafts coupled togetherby a set of gears operable within `and interconnected Vto a'iluid-tightcasing, such casing being fixed to androtatable with one of said powershafts. The casing contains a non-compressible uid, preferably alight-grade lubricating oil, and

usually includes valve-controlled ports providing for controlledcirculation of fluid through other parts of the transmission.

The control valve governing these ports inthe casing performs thefunction of the clutch as well as some of the functions of the gearshift device, ordinarily employed with conventional transmissions.Gperation thereof regulates the passage of fluid through the circulatorysystem of the mechanism, and causes gradual transition between neutraland speed reduction, overdrive,

or reverse. Y

The set of gears within the casing is arranged to function -as a fluidpump when permitted. Thus, when the power output shaft is under loadandthe circulatory system proper of. thetransmission is `short-circuitedby reason of the control y-valve being in its neutral position-iluidthereby beingrallowed to circulate only locally `between the said portsby way of the control 'valvethe motion -of the kpower input shaft v.is

entirely spent in ineffective pumping of the uid through the localizedflow circuit. When, however, the control valve is positioned to closesuch direct intercommunication of the said ports, and conditions inother parts of the transmission are such as to prevent any circulationthrough the system, the gear set within the casing is not permitted torotate freely as a field pump, and such gear set, the fiuid bodysurrounding it, and the enclosing casing act as a rigid unyieldingcoupling between the two power shafts, transmitting rotative motion fromone to the other in a direct `drive relationship. Between these twoextremes is a partial direct and partial fluid drive relationship,wherein the gear set has limited freedom of rotation within its casingas a fluid pump. Such relationship is expressed in terms of reducedspeed between power input and power output.

Under such condition of operation, it is a feature of the invention thatthe energy represented by the `difference between input speed and outputspeed is transmitted to the power output shaft in terms of increasedtorque. For this purpose there is provided in the transmission, inassociation with the power output shaft, a second gear set of variablecapacity which is adapted to act as a gear motor relative to the poweroutput shaft. Fluid pumped by the first gear set is conducted to thesecond or variable gear set by the fluid circulating system, where ityacts to drive the latter and, thus, the power output shaft. Controlmeans is provided to afford infinite variation of the capacity of thesecond gear set, within its design limits, in accordance with the driveratio appropriate under any given operating condition.

Since the second gear set is variable in capacity, and may be adjustedso that lcomponent gears thereof are entirely out of mesh, it isdesirable to provide timing means for maintaining the mechanism inperfect adjustment. This advantageously takes the form of a third gearset associated with the power output shaft.

In accordance with one aspect of the invention, this third or timinggear set is also utilized as a gear motor, auxiliary or secondary to thesecond gear set, for impressing the said energy differential upon thepower output shaft in terms of increased torque. The capacity, then, ofthis third gear set, acting as an auxiliary gear motor, added to thevariable capa-city of the second gear set, acting as a primary gearmotor, increases the practical range of drive or speed variationafforded by the transmission. To this end, control means is provided forbringing such third or timing gear set into the system as an auxiliarygear motor.

In addition to the relationship resulting in infinitely variable reducedspeed ratios between power input and power output, the structuralarrangements outlined above, provide for operative relationshipsresulting in infinitely variable overdrive ratios and infinitelyvariable reverse-drive ratios.

For overdrive ratios, the control valve is positioned in such manner asto connect the high pressure side of the first gear set with the highpressure side of the second gear set. Under such conditions, if thefluid capacity of the second gear set is less than that of the first,the second gear set acts as a, fluid pump rather than a fluid motor. Thefluid then pumped by the second gear set causes the first gear set toact as a motion superimposing additional rotative motion upon thealready rotating output shaft, that is to say, the power outputcomponent of the coupling between the two power shafts is stepped up torotative speeds higher than respective rotative speeds of the powerinput component. Variation of overdrive ratios is accomplished by thesame control means previously mentioned in connection with variation ofreduced speed ratios.

For reverse-drive ratios, the control valve is positioned in neutralduring the time required for the above-referred-to control means toplace the second and third gear sets in condition of maximum capacity;whereupon it is moved to overdrive position. Operating as gear motorsunder these circumstances, the second and third gear sets overcome anytendency toward direct drive from power input shaft to power outputshaft and effectively rotate the power output shaft in reverse.Variation of reverse-drive ratio is accomplished through the saidcontrol means by decreasing the capacity of the second gear set.

Of the two independent but coupled power shafts provided in thetransmission, either may be used as the power input shaft or the poweroutput shaft, with, however, somewhat different results being producedby the two opposite uses. For most uses, that one of the power shaftswhich is rigidly fixed to and rotatable with the fluidtight casing willbe taken as the power output shaft, with operative results as abovedescribed.

Of the severa-l gear sets the first is planetary, embodying one or moreplanet gears journaled to the interior walls of the fluid-tight casingand in mesh with a sun gear which is fixed to one of the power shafts.The casing is fixed to the other of the power shafts, and when not indirectydrive relationship, the planet gear or gears revolve about therotating sun gear. Such planetary gears are adapted to act as a motor,in overdrive for instance, for driving the casing and the power outputshaft to which it is attached, at a speed greater than that of the powerinput shaft.

The second or variable gear set embodies a gear fixed to the same powershaft that the said fluid-tight casing is fixed to, and includes one ormore gears normally in mesh with the fixed gear but movable relativethereto axially for varying the degree of mesh, preferably fromsubstantially complete disengagement to full meshing engagement. Plungertype actuating mechanism hyldraulically controlled is advantageouslyemployed to move the movable gear or gears longitudinally of the axis ofthe fixed gear into any desired degree of intermesh, thereby achievingany desired drive ratio for the transmission as a whole within itsdesign range.

The third or timing gear set, corresponding in general with the variablegear set which it must keep in adjustment, is of fixed or constant mesh.It may be variously formed and arranged relative to the variable gearset, depending upon the performance desired from particular embodimentsof the transmission. Thus it may be arranged to operate as an auxiliarygear motor o1' pump, as previously mentioned, or it may be given only atiming function.

'I'he control valve of the transmission and the fluid circulatory systeminvolve novel features of fluid flow control and utilization which areespecially advantageous in correlation with the respective sets of gearsoutlined above. Furthermore, the gear tooth arrangement and designprovided for the respective gears of the second or variable capacity setis such as to effectively i either manual or automatic control.

y'seal against liiuid flow axially :of said igeans between inter-meshingteeth thereof at all Vthe various positions of fvinterrnesh. i

To provide such a transmission Iwhich makes possible the consistentoperation of lan internal combustion engine high lon its torque curvefor the sake of economy `of operation, :without the sacrifice of suchflexibility of operation as is ordinarily obtained by havingconsiderable yexcess torque available.

To make possible more satisfactory and easier operation and control ofan automobile, with kless fuel consumption than heretofore, andtherefore, at lower cost. f

To provide a sturdy and compact infinitely variable transmission whichis relatively inexpensive to construct and which is adapted to becontrolled hydraulically.

The above and further objects and features of the invention will befully considered inthe folylowing detailed description of the severalpreferred constructions illustrated by way of example only, in theaccompanying drawings.

In the drawings:

Fig. l represents a sideelevatiom partially in section, of an entiretransmission mechanism constructed in accordance with the invention;

Fig. 2, a horizontal section'taken on the line 2 2, Fig. l, certain portholes having been arbitrarily moved to the section-plane;

Fig. 3, a vertical section taken along rthe line 3 3, Fig. 2;

Fig. 4, an elevation of the transition plate of the gear casing, whichis provided with ports for conducting fluid from the rstgearset orpumpof Fig. 3, the view being taken approximately on the line 4 4, Fig. 2;

Fig. 5, an elevation of the control valveldrive mechanism as viewed fromthe Iline 5 5, Fig. 2, with the shaft and ported transition piece andall forward mechanism removed; v f

Fig. 6, a vertical section taken alongthe line 6 6, Fig. 2;

Fig. 7, a vertical Vsection taken along `the -line 'I I, Fig. 2; p

Fig; 8, a fragmentary longitudinal section taken along the line 8 8,Fig. '7

Fig. 9, an enlarged fragmentary section of meshing gear teeth of theintermeshedvariable mesh gears of Fig. 7;

Fig. 10, a vertical section taken' alongthe line Ill-I0, Fig. 2;

Fig. 11, half of thesymmetricall vertical section taken along the lineII I I, Fig. 2, `see also the line II-I I, Fig. 12;

Fig. 12, a longitudinal vertical section taken along the line I2 I2,Fig. 1l, with the center gear of the timing set removed;

Fig. 13, half of thexsymmetrical end elevation of the transmission asviewed fromfthe right in Fig. 2, with the rear cover. plate removed'to-show the Icy-pass valve, see the line I3 I/3,;Fig. 2;

Fig. 14, a. longitudinal verticali section taken valong the line I4 I4,Fig. 13, the by-pass valves being shown closed; 3 I

Fig. l5, a fragmentary verticalsectionftaken along the line I5 I5, Fig.2;

Fig. 16, a fragmentary longitudinal section vthrough. the control valve:takenalong the line '.I:6 II6,.Fig. 15;

- Fig. 17, a fragmentary vertical section through thecontrol rvalve Vastaken .along theline I'I `I 1, Fig. 16, the valve being in its neutralposition;

Fig. 17A, a view similar to that of Fig. r17 except that lthe valve isin reverse or overdrive Iposition;

Fig. 17B, a view similar to that of Fig. 17 except that the valve is inlforward drifve position;

Fig. 18, a fragmentary Vertical section through 'the ycontrol valve astaken alongthe line I8 I8, Fig. 16, the valve being `shown in itsneutral position;

Fig. 18A, za View zsirnilar .to thatfof Fig. :18 -except that the valveis in reverse or overdrive position;

Fig. 18B, a view similar to that of Fig. 18 except that the valve is inforward drive position.

Fig. 19, a fragmentary horizontal section corresponding to that of Fig.2 but illustrating only the extreme rear sections of an alternateconstruction in which the timing gears are not used as an auxiliaryfluid pump; and

Fig. 20, a fragmentary horizontal section corresponding to that of Fig.2 but illustrating all but the extreme forward section of an alternateconstruction arranged for manual control.

Referring now to the particular form of the 'invention illustrated inFigs. 1 through 18B, the

fundamental elements thereof can all be seen in Fig. 2. They are thethree sets of gears I, 2 and .2; 3, 4 and 4'; and 5, Band 6'; and therotary valve 'I. y

The sets of gears yare all shown in section on one side of the centrallongitudinal axis of the transmission and in elevation on the other.Those variation.

The gear set positioned to the left in Fig.` 2, which may be consideredthe forward or first set, consists of a center gear I and two gears 2and 2.

-Since it is primarily by control of the relative Yor sun gear I ismounted on a. shaft to which Ait is secured against rotation. by helicalsplines set in helical keyways 9.k These splines and correspondingkeyways 9 have the same lead as the helical teeth of gear I, therebyallowing gear I to,h float freely in its housing while transmitting endthrust, as well as torque, to the shaft 8.

The shaft 8, serving for purposes of this description as the power inputsnafu-though atcertain times capable of serving also as the power outputshaft, enters the transmission housing through front cover plate I 0.Fluid is prevented `from leaking outaround the shaft by the provision ofa seal ring I I held by a sleeve I 2. The sleeve I2 also holdsradial-thrust bearing I3 in place against a shoulder IIla of the plateID. The entire assembly is held in place by the nut I4.

The hub of an impeller wheel I5 serves as a spacer between the bearingI3 and a shoulder on the shaft 3. This impeller I5 has radial fins I6 onits forward face, and is secured to rotate withthe shaft kIl. The lockednut I1 holds the innerA race of the bearing rI3 against the hub oftheimpeller.

The casing of the set of controlled planetary gears is composed of afront platey I6, an intermediate section I9, and a back. plate 20. Theshaft 8 is journaled at the center of the plate I8, and also at thecenter of .plate 20, as shown. 'I'he casing section I9 closelyencompasses the gear set I, 2 and 2, and as shown in Fig. 3 enables itto act in a pumping capacity in association with diametrically oppositeports A and A' and B and B formed in the back plate 20. Passages 22 aredrilled progressively from one end of the gears 2 and 2 to connect alldiametrically opposite tooth spaces of such gears, for the purpose ofbalancing pressures and of floating the gears in the housing. Similarpassages are drilled in gears 4, 4', 6

yand 6'.

The back plate of the casing is rigid with and conveniently an integralpart of power output shaft 2|, and, as illustrated in Fig. 4, serves asa Vtransition piece between the fluid pump, formed by the controlled setof planetary gears I, 2 and 2', and the valve 1. It carries fluid fromthe ports A and A', Fig. 3, to an inside annular opening C around theshaft 2 I, and from the ports B and B to another annular opening D. Ofthe channels AC, AC, BD and BD through which these connections are made,AC and BD are here arbitrarily rotated into the picture plane of Fig. 2to better illustrate the arrangement.

The planet gears 2 and 2 rotate on shafts 23 and 23', respectively,which extend between and are supported by the plates I8 and 2D. Ihe gearcasing, made up of the separable elements I8, I9 and 20, is fluid-tight,and is held together by bolts 24, Figs. l and 3, which also act asdowels to locate and support the casing section I9. Lips Ia and 20a,formed around the periphery of the respective plates I8 and 20, see Fig.2, serve to additionally support casing section I9.

The nuts 26 on bolts 24 are covered by an appropriately recessed plate21, Figs. l and 2, which is secured to the plate 20 by screws 28. Theplate 21 eliminates .any churning action between nuts 26 and the headsof bolts 29, which bolts secure an outer housing 30 to the rear or backportion of the transmission. Such outer housing 30 fits into the innerface of the front cover plate II), and is fastened to it by the screws3I. Together, the housing 30 and cover plate I0 provide a reservoir offluid in which the impeller I5 builds up various pressures dependingupon the speed of rotation of the shaft 3.

In Fig. 5, wherein the inside rear wall of the housing 36 isillustrated, portions of the drive for the rotary control valve 1 areshown. In this particular transmission, such drive is hydraulic. Theflanged periphery 1a of the valve 1, where it enters the housing 30, istoothed to mesh with the worm 32 of the drive. The shaft 33 on which theworm 32 is mounted is journaled in the bearings 34 which are attached tothe housing 30, as shown. Also mounted on the shaft 33 is a spiral gear35 which meshes with another spiral gear 36. A recess 31, milled intothe wall of the housing 30, gives clearance for the worm 32 and gear 35.

The spiral gear 36 is pinned to a shaft 38 which extends through therear wall of the housing 30, see Fig. 6. Here it is keyed to a gear 39in mesh with a gear 40, forming a gear motor which is driven by fluidsupplied through ports 42 and 43, shown as tapped holes in Fig. 1. Thesegears have pressure. balancing passages (not shown) similar to thepassages 22 which float the gears in their housing. Around the end ofthe small gear motor 39, 40, the housing 30 is secured to a section 44of the rear housing by screws 45. In place of two of the bolts 29, whichwould otherwise flll the space occupied by the gear motor, long studbolts 46 are used.

As shown in Figs. 6 and 17 passageways ED, ED, FD, and F'D are adaptedto connect the chamber D of rotary valve 1' at the illustrated positionof such valve, with those respective longitudinal channels E and E and Fand F which extend through housing sections 44 aand 48.

As shown in Fig. 18, similar passageways EC. E'C, FC and FC are adaptedto connect the chamber C (through C) of the rotary valve 1 withrespective longitudinal channels E and E' and F and F at other positionsof the valve 1 as illustrated in Figs. 18A and 18B.

In the housing section 44 and the adjoining housing section 48, atopposite sides of rotary valve 1, are provided mutually similarcylinders P and P', see Fig. 2, within which operate the respectivepistons 41 and 41'. These pistons move to the rear out of housingsection 44 and into housing section 48, where they cover therespectively adjacent face portions of gear 3 of the variable or secondgear set, as piston 41' is shown to be doing in Figs. 2 and '1.

A shaft 49, shown integral with the gear 4, Fig. 2, of the second gearset, passes through and is journaled in the rear end of the piston 41.The piston 41 is held against the forward end of gear 4 by the lockednut 50, which is screwed onto the end of the shaft 49 and transmits endthrust from the gear 4 to the thrust bearing 5I. To the opposite end ofthe gear 4, the threads 52 secure a collar 63 which makes a rotating tin section 54 of the housing and seals the ends of the gear teeth.

The collar 53 and the rear of the gear 4 make a sliding t on a helicalsplined shaft 55. Where the shaft 55 passes through the divider plate 56in the housing, the splines are turned off and a split collar 51 issecured thereat to provide a smooth bearing surface. Beyond the plate56, the shaft 55 extends into section 56 of the housing, where it issecured to the gear 6 of the third or timing gear set. A reduced section59 of the shaft 55 is journaled in the rear section 60 of the gearhousing.

Through the shaft 55, the gear 6 acts as a timer for the gear 4. Forthis purpose, the helical splines on the shaft 55 have the same lead asthe tooth helix of the gears 4 and 6.

The piston 41 and gears 4' and 6 involve similar construction at theopposite side of the transmission.

The shaft 2I is journaled in the rear of housing section 44, in thefront of housing section 54, in the spacer 56, and in the rear housingsection 60, as shown in Fig. 2. The gear 3 of the second gear set issplined to the shaft 2I on the helical keys 6I positioned in helicalkeyways 62, as shown in Figs. 2 and '1. The helix formed by the keys 6Ihas the same lead as the tooth helix of the gears 3 and 5 of the firstand third gear sets, respectively. As shown in Figs. 2 and 11, the gear5 is splined to the shaft 2| by the helical keys 63 positioned inkeyways 64 which are continuations on a smaller radius of the helicalkeyways 62.

The thrust bearing 65, Fig. 2, positioned on the shaft 2I by the lockednut 66, transmits end thrust from that shaft to housing section 54.

Where the shaft 2I leaves the rear of the hous- 9 ing it passes througha seal ring 61- which isV held in place by the rear cover plate B8.

The bolts 29 and 46Y which hold the transmission together, also serve asdowelsY to position various parts of the housing relative to others, andto enable the rigid sections to reinforce and support the more flexibleones.

It is to be understood, of course, thatthe housingof the transmission,madelup'a's it is of the several parts 18,38, 44, 4,8-, 54, f, 58,'50andB8, in the manner herei-nbefore described, does notvrotate. It forms astationary component of any installation of which the transmission `s aypart.

Thegears 4 and 4, arranged as they are in combination with the pistons4.1r and 41` and sealing collars 53 and 53', form a` variable capacitypumping unit with the gear 3. The pumping capacity of either gear 4 or4' depends. upon how much of its gear face is in meshI with the gear 3.i

To prevent what otherwise would be leakage of fluid by ow longitudinallybetween inter# meshing teeth which would weave or lace at the ends ofsuch teeth between the two longitudinal channels formed by the teeth,helical gears are provided. Such gears advantageously have gear teeth soformed that in the combination of various cross sections taken in axialprogression along the Zone of gear intermesh, (which in this case differfrom one another due to the change in phase of intermesh caused byadvance along the tooth helices), a closed envelope is` provided by thelines of contact between the teeth. As'hereinafter set forth in moredetail, helical teeth formed with negligible running clearance and withnegligible backlash provide such closed envelope.

This arrangement cannot provide acomplete seal under all conditions. Forinstance, when the gears are out of mesh, as gears 3 and- 4 are shown tobe in 2, there is no tendency for them to pump. There is however amaximum tendency for iiuid leakage by weaving or lacing between theadjacent tooth ends. In this oase the open areas between what would becontact points if the teeth were in mesh represent simple oridcesthrough which leakage could take place. In the present embodiment of theinvention leakage is prevented by wing extensions on the respectivepistons, see the wing extensions 4T'a of piston 41', Fig. 7. Whenv thegear 4, or 4', is out of mesh, the wings of lpiston 4lI or pistonl 41'completely seal the ports El and F, or

rE' and F', by covering the lateral outlets therefrom, see especiallythe outlets EO, Eig. 8. n

As part of their sealing function, the wing ex. tensions on the pistons41 and 41 extend the surfaces of arcuate recesses 41h and 4l'bin thesepistons, These surfaces make slid-ing contact with the tooth tips ofthat portion of the gear 3 not meshing with the respective gears 4 or4',

and are extended beyond the lines of intersec-v tion of the addendumcircles of the gears 3, 4, and 4', so that there will not be diagonalopenings for leakage across said surfaces through the tooth spaces ofthe non-meshing portion of the gear 3., even though the teeth oi thesegearsl may be cut on relatively steep helices.

When either of the gears 4 and 4f is vcom` gears are only partially meshnecessitatesthev provision of helical gearsvvhose gear teeth have,

negligible backlash and` negligblerunning clealance vand are otherwiseformedl to seal againsty axial leakage through the spacesA betweenI.I1.@..S.1,1.'Y

ing teeth.

When the teeth of ordinary power transmis,-

sion gearing pass ythrough their mesliinglfcycle,`

tooth contact is first made when a point ynear the base on the forwardvflank` 0f thel driving tooth touches a point near the tooth tip on therear face of the driven tooth. Assuming gear 4in Fig. 9r to be thedriving gear and to, be`

rotating in a clockwise directionk as. indicated,v this contact wouldoccur at thepoint X, As thel teeth pass through their meshing cycle,this con-l tact point progresses. down the rear face toward the base ofthe driven vtooth and up1 the for.

ward` flank toward the tip of,` thisdriving to,oth.

This is the only point of contactnecessary for the action of the` gearteeth.

The tooth outline, utilized in accordance with:

this invention is such that there are other points of tooth contact, orat least points of close enough proximity `to `serve as hydraulic seals.@ne of these seal points originatesV at the, point of first contact, butduring the meshing cycle it moves,

on the tooth surfaces in a direction opposite the direction :of themotiony of the pressure point.- This seal pointlr moves, withoutlDpreciable ih terruption, around the root of the driving tooth to `thedank of the tooth ahead, andron. the surface of the driven tooth,` itmoves across., the tipto its opposite, or forward, face during theImeshing cycle.

These teeth are out not only ,with negligihle: running clearance to makeit possible 12.0A carry,

the rear face of the drivingv tooth to a pointr near the base of thattooth, where it meets the.

seal point originating atV the point of nrst contact on the drivingtooth behind it. This meet,- ins takes place at, the point wllerercontactingtween the teeth is broken, see point Y, Eig. 9. The other sealpoint originating from this division moves forward around the tip of thedrivi ing tooth and across the root of the driven `tooth to meet thepressure p oint on the tip of the front face ofthe driving tooth at theSeCOIld point where contact is broken. In the cross-section shown inFig. 9, there` are live seal points in transition,` along thel surfaces.

of the gear teeth. These pointsare locatedapproximately at the points,U,` V,v W, and Y, The original contact point X is, in the process ofdividing into two'points, one of which will move around to join thepoint V. The points V and U both originated at the points marked UV.,"Ijhev-- point U is moving to join the point W. Two seal points havejust joined at theY point Y, where con; tact will be broken. One ofthese points located at Y originated with W at the points. marked YW.

The result of using helical teeth of this spe-A cial outline can bevisualized from Fig. 9.. Since at progressive sections along the axis ofthe gears the teeth will he in progressive phasesof. intere:

mesh due to their advance along the helix angle, the contact or sealpoints will form a seal line which will progress around the toothsurfaces and effectively seal off one of the two openings, between Y andW or between V and X depending upon the direction of the tooth helix,against axial ow of fluid.

It will be evident that there must be enough gear face in mesh topresent a certain minimum advance along the tooth helix. It will also beevident that there must be a sufficient number of teeth on the meshinggears to insure enough teeth in mesh, at any given time that a seal willbe established behind an exposed tooth end before, or very shortlyafter, the seal ahead of it is broken.

It should be noted that the sealing envelope formed by the seal pointsis of a transitory nature and shifts along the gear teeth as they passthrough their meshing cycle. Thus, it acts as more than just a staticseal. In shifting along the teeth it carries fluid with it, thus causinga controlled flow of fluid along the spaces between the meshing teeth.It is desirable from the standpoint of volumetric emciency that as muchof this flow as possible be directed toward the port from which the gearteeth enter into mesh. It will also be evident that the channels throughwhich this controlled ow takes place must present sufficient opening toprevent trapping or cavltation. A

It is characteristic of these gears that a small amount of fluid will betransferred past the exposed tooth ends in a direction counter to thenormal transfer of fiuid by way of the gear tooth spaces. This fluid isthat which otherwise would have been trapped against the end wall. Itsamount depends upon the characteristics of the gear teeth. Actually forsome tooth forms it is an almost insignificant quantity.

This flow will reduce the displacement volume slightly, but it does nottheoretically represent a loss of energy since flow does not take placeby leakage but rather by positive pumping or motor action.

Several tooth outlines may be satisfactory for this sealing purpose. Theteeth need not be self driving, since the variable mesh gears 4 and 4are always driven by the timing gears 6 and 6. The particular tooth formshown in Fig. 9 is a modified involute consisting of involute curves onthe working faces, curves making an appropriate gradual transitionbetween the involute curves and the addendum circle at the tooth tip,and other curves extending between the bases of adjacent teeth, suchlatter curves being formed to fit the envelope of the meshing tooth tippassing through its meshing cycle. The said envelope, it should benoted, is the imaginary outline generated in the rotating plane of thegear under consideration by a tooth tip of the respective meshing gearpassing through its meshing cycle. As aforestated, in this designcontact is made approximately at the point X, such contact point thendividing and running along the surface of each tooth to unite and breakapproximately at the point Y. The word contact is used here to meanssufficiently close proximity to cause an effective hydraulic seal, andnot necessarily metal to metal contact.

Since these variable mesh gears are not always operating far enough inmesh that there is the necessary one-half tooth interval of advancealong the meshing helix, the fact that this tooth outline also providesareas of c1056. QnaC? well as a continuous line contact is a decidedmember is contained in an annular space formedv between the cylindricalinner wall 44a of housing section 44 and a cylindrical sleeve 69 whichis secured in section 44 of the housing by screws 10. There is acircular opening 30a in the back wall of housing section 30, which formsa continuation of the said annular space and accommodates the forwardportion of the valve. A forward wall end of the valve 1 is steppedbackwardly relative to the forward end of the sleeve 69 so that bothmake sliding contact with rear surfaces of the transition piece or backplate 20. These contacting surfaces provide rotating seals betweenannular chambers C and D, chamber C being formed between shaft 2| andsleeve 69, and chamber D between spaced walls of the movable valvemember itself.

On a plane passing through the center of the back Wall of the forwardhousing section 30 parallel with the wall faces thereof, see Fig. 15,there is a passage 1| which terminates at one of its ends in a tappedhole 12, and opens against the outer surface of the valve 1 at its otherend. In the same plane there are six holes 13 through the outer wall ofthe valve 1, and so located that they will provide communication betweenthe annular chamber D and the tapped hole 12 only when the valve 1 is inthe position shown, or has been rotated in either direction by somemultiple of 60. Through the tapped hole 12 a connection may be made to afluid pressure source whereby, through valve mechanism not shown,control of the supply of fluid to gear motor 39-40 may be effected, itbeing noted that such gear motor 39-40 rotates valve 1. The valvearrangement may be such that, when one of the holes 13 is in registrywith passage 1|, the supply of fluid to gear motor 39-40 is cut off,thereby halting rotation of valve 1.

In the same plane, another passage 14 terminates at its inner end in anarcuate slot 15, which extends slightly more than 60 around the surfaceof the valve 1. Through this slot 15 and the holes 13, the passage 14maintains continual communication between the chamber D and the tappedhole 16.

Another passage 11, shown in Figs. l5 and 16. runs from the annularchamber C along the outside of the bushing 18 and out through the rearWall of the housing section 44 to the outlet 19, Fig. 1.

A wall 80, Fig. 16, in the annular chamber D of valve 1 divides off arear chamber C which serves as an auxiliary to the inner chamber C.' Oneither side of the division there are ports cut in the sleeve 69, thevalve 1 and the housing section 44. The relative positions of theseports when the valve 1 is in neutral position, is shown in Figs. 17 and18. Figs. 17A and 18A show the relative positions vi'hen the valve 1 hasbeen rotated 60 clockwise (considered from the standpoints of Figs. 5and 15) from the neutral position. Figs. 17B and 18B show the relativepositions when the Valve 1 has been rotated 60" counterclockwise fromthe neutral position.

In this form of the transmission, the gears 5, 6, and 6 serve not onlyas timing gears to keep the ngears 4, and 4' rotating in propersynchronism with gear'31wh'en-they are out of mesh or to drive the gears4 or 4' when they are noti section 54 of the respective channels E,E'QF.'

and. F', Fig. 7 in housing sectionsAli and, 48.

Through the respective intermediate passages- I,

I', J\ andJ', Figs. 11. and 12, the passages G,. Gf, l-I and H'communicate With the portsfNr N ,0

and O respectively, ofthe timing gears G' and.

Si'. (Since only the right half of housing sections 53 and 6.5kareillustrated in Figs. 1l andA l2, the ports N and O' and. the passagesI.' and J do. not appear. The, portions Vnot showny are, however,duplicates of the illustrated. portions. of similar designation.)

Through the forward wall of the'rearmost housing section 69, the portsN, O and N', O communicate with the chambers K and K', respectively, seeFigs. 12e and i4, also Fig. 2".

In alignment with the passages G, G', H and H', there are cylinders L,L', M and M' located in section 58' of the housing. The pistons 8l,operable within theserv cylinders, are mounted on rods 82 whose forwardends pass through bushings in the wall 56', and thus into the respectivepassages H, H', G and G1', inv which they are secured to respectivepiston valves k83. The opposite ends ofy these rods 82 pass `thnmghsimilar bushings in the rear wall of housing section 58I` and thus intothe chambers K and K', where they are attached by the screws fifi to theplate valve 85 in such a manneras to form a sliding hinge j oint whichdoes not force the pistons 31 to move simultaneously. y

A system of passages 86"; which communicate with the outlet 8l, Figs. l,2 and ll, interconnects the forwardv ends of the` four cylindersV L, L?,M and M. 88, which communica-tesV with the outlet $9, Figs.

1 and 13, interconnects the rearends` of these cylinders. Y

The operation of the above valves can be seen from a comparison of Figs.12 and 1'4. In Fig. 12 the pistons 8'! are at` the. rearv of theirtravel.v The. ports N and O communicate throughthe chamber K and aresealed off from the channels H and G by the piston valves 83. Through.the chambers K, fluid pumped by the gears 5, 6, and 6" flows freelybetween the ports N' and' O when the pumping capacity of these gearsisnot being utilized. In Fig. 14 the pistons 81 vare at the forward endof their travel, and the ports N and' O communicate with they passagesGrand All the'voids in the transmission arerllled with a fluid,preferably a light grade' lubricating oil, which serves as lubricant,hydraulic media, and control fluid. There are several external controlconnections for duid flow in addition to those already mentioned. Theseconnections 'are shown in Fig. 1. The outlet .90 communicates throughAnotherV simi-lar system of' passages' loy the plate lol with the:spaceneawhs imlosoffthev impeller disc4 l5. The outlet 9lpasses throughtheV outer walls of the casing; 30 to,` the interior thereof. 'IheYoppositely disposed outlets 92 and- 92', Fig. 6;, connect. with theforward' ends of the chambers Pb and P', respectively.A The oppositelydisposed inlets 93;, Fig. 1', and 93' (onlyi tothe power output shaft 2lthrough the platey 20, is restrained from moving, there is a tendencyfor the planet gears 2 and 2' ofthe iir-st gear set to rotateiin aclockwisedirection, and for the flu-id pressure in the ports A and A" toincrease above the pressure in the ports B and B.r g Y As previouslydescribed, the A portsfcommunicate with the C chamber and the B portscommunicate with' the D- chamber. When the valve 1 is in the neutralposition of Figs. 17. and 18,

there is direct communication between the C and the shaft 3 and.associa-ted sungear I are freey to rotate, without, in turn, rotatingthe said cas ing and the power output shaft 2 l.

When the valve 'I is in this neutral position',

there is also direct intercommunication between the severalY ports E andF which hand-le theV fluid being pumped by the variable gears and thetim.-v ing gears associated with power output shaft 2:1,

such direct intercommun-ication providing freey ated gears might be.

If, while the input shaft 8is beingy driven asin- Y dicated, the valve 1is slowlyrotated through 60 in a counterclcckwise direction (consideredfrom the standpoint of Figs. 17 and 1S) to the position shown in Figs.17B and 18B, the free communication between valve chambers C* and D, andtherewith` between' the ports A and B', is closed. At the same time, theA and A' ports are brought into communication with the F andgF' ports,through the C and C' chambers, 18B, while the B and B ports are broughtinto communication with the Ejand E' ports, through the D chamber, Fig.17B. A study of the ports in the valve 'I' will show that thistransition isl made gradually. The gradual transition between neutraland a driving position provides a smooth clutching action between theinput and outputI shafts; the energyv represented by slip duringclutching being converted to heat by throttling fluid through theclosing ports.

When the valve T is in this position, any yfluid.

duced speed, from the power input shaft 8 `to the" power output shaft2|. The gears 2 and 2' will transmit torque of the shaft 8 directly tothe shaft 2| through the casing |8| 9-20. The balance of energy,represented by the limited rotation of gears I, 2 and 2 relative totheir enclosing and power-transmitting casing and by the fact that theshaft 2| turns at a lower speed than the shaft 8, will be transmittedhydraulically back to the gears 3, 4 and 4 of the second gear set, or tothe gears 5, 6 and 6 of the third gear set, where it will be impressedupon the shaft 2| in the form of increased torque.

With helical pumping gears, an unbalanced hydraulic pressure in the gearhousing tends to offset the end thrust from the tooth pressure and tofloat the gears axially in the housing. However, since the end sections53 and 53 of the housings for gears 4 and 4, respectively, are free tomove with those gears, there will be a resultant end thrust,proportional to the end thrust from tooth pressure, which will tend tomove these gears and associated structure axially in the housing. Anexamination of Fig. 2 will show that in transmitting a counterclockwisemoment (considered from the right or rear end) to the gear 3, the gear 4will develop an end thrust toward the right or rear end of thetransmission. Control of the transmission ratio is accomplished bybalancing this end thrust against hydraulic pressure built up in thechamber Q through the inlet connection 33.

The sequence of operation in progressively reducing speed is initiatedby increasing the pressure in the chamber Q, by suitably introducingfluid through the inlet 93, until the gear 4 is completely in mesh withgear 3, which occurs when the pressure in Q reaches a set fraction ofthe difference in pressure between the A and B ports. Thereuponintroduction of fluid into the chamber Q' through the inlet 93', willforce the gear 4 into mesh with gear 3. When the pressure in Q reachesthe set fraction of the pressure difference between the A and B ports,introduction of control fluid to the rear of the cylinders L, L', M andM through the inlet 89 will force the pistons 8| forward, openingcommunication between the channels G, G', H, H' and I, I', J, J',respectively, and bringing the timing gears 5, 6 and 6 into action as agear motor. Simultaneous release of the pressures in chambers Q and Qwill let the gears 4 and 4 move back out of mesh so that theirfunctional capacity is taken over by the timing gears in a relativelysmooth action. Increased functional capacity may be then obtained byforcing gear 4, and then gear 4', back into mesh in the same manner asbefore.

Wherever mention is made in this text of causing axial motion byintroduction of fluid into one chamber, it should be assumed thatsuitable relief is provided for fluid in the opposing chamber.

Equating the amount of fluid flowing through the variable capacity gearsto that flowing through the fixed capacity gears gives a simpleexpression for the speed relationships in this transmission. The speedof rotation of the shaft 2| (R21) multiplied by the active fluidcapacity per revolution of the variable capacity gears and the timinggears (C2i), expressed in terms of the fixed capacity of the controlledgear set 2 and 2', equals the difference between the speed of rotationof the shaft 8 (Rs) and the speed of rotation of the shaft 2| (R21),multiplied by the capacity of the gear set 2 and 2 (Ca), or:

or the reduction ratio Re Ced-Cs This expression shows how increasingthe active capacity of the variable capacity gears causes an increase inthe reduction ratio between shaft 8 and shaft 2|.

In the transmission shown, the sets of gears 3, 4 and 4 and 5, 6 and 6',combined, have three times the pumping capacity of the first set ofplanetary gears 2 and 2. The lowest gear ratio, then, occurs when thedifference in rotative speed between power input shaft 8 and outputshaft 2| is three times that of power output shaft 2|. Substituting inthe speed ratio equation shows that there is a four to one reduction atthis lowest gear ratio:

When the timing gears 5, 6 and 6' are not pumping and the variablecapacity gears 4 and 4 are both out of mesh with the gear 3, no fluidcan flow between the F ports and the E ports, and the gears 2 and 2 ofthe first set cannot rotate Within and relative to their enclosingcasing |8-|9-20. The transmission is then in direct drive, lwith all thepower transmitted mechanically.

If, While the transmission is in this direct drive relationship and nofluid is flowing, the valve l is rotated a little more than 30 in acounterclockwise direction from the position illustrated in Figs. 17Band 18B, it reaches a position where.

communication to the F ports is completely sealed off. 'Ihis is not oneof the essential operating positions since the E and F ports areautomatically sealed off by the pistons 41 and 41 and the piston valves83 when in direct drive. However, since it provides a sealed directdrive in which only the low pressure from the B ports reaches the rearportions of the transmission and all leakage losses are eliminated, itcould be used as an operating position to give a very efcient directdrive where such a drive was to be used a large portion of the time. Toenable the controls to stop the valve 1 at this position, thediametrically opposite holes 94, shown dotted in Fig. 15, may be added.

If the counterclockwise rotation of the valve is continued until ittotals 60 from the position shown in Figs. 17B and 18B, it will be asillustrated in Figs. 17A and 18A. There the A ports communicate with theE ports through the C and the C' chambers, and the B ports communicatewith the F ports through the D chamber. In

Fig. 'l it can be seen that the high pressure froml the A ports, whenapplied to the E ports, opposes the counterclockwise rotative drivewhich the planetary gear set I, 2 and 2 transmits directly to the shaft2| through the casing |8|92|L As long as the variable capacity of thesecond gear set 3, 4 and 4' is not increased to equal or exceed thecapacity of the first or planetary set, this opposing torque is notgreat enough to stop the counterclockwise rotation. The variablecapacity gears 3, and 4 or 4' are therefore taking power from the shaft2| to pump fiuid through the E ports to the A ports of the first gearset.

The result of this fiow can be seen in Fig. 3.

The flow into the A ports causes the planet gears the speed ratioequation, the capacity Czllof the variable capacity gear rset is given anegative value. The range of overdrive is theoretically infinite. In thetransmission illustrated', only one of the gears 4 or 4 is usedVand,since this one gear has three-.fourths the capacity for the first gearset, the maximum overdrive ratio is to one,-as the equation will show:

=cll+c= :l l( Reduction) k Os C3 4,

RB l e Control in overdrive is accomplished the same as in speedreduction exceptthat, since the end thrust on the gear 4 or 4 isforward,V the control fluid isintroduced through the inlet 92 or 92',

(Overdrive) 2| with equal nexibinty, but with somewhat -differentcharacteristics. .Shaft 8, then, of cours .becomes the power outputshaft.

The impeller l5 serves several purposes. It builds up a centrifugalpressure in the fluid reservoir formed by casing 30 and cover plate I0.Such pressure exceeds the pressure at'the cony nection 90 (which may bevented to the atmosvfour Fig, 1, intothe P or P- chamber, instead ofintov the Q or Q' chamber. It will :be noted that con-l trol pressurewhich, in reduction, would force the twocontrol gears farther into mesh,and in over drive, would force themfarther out of mesh, will in eithercase cause a reduction of gear ratio.

From the position illustrated in Figs. 17A Vand 18A, the valve 'I canYbe rotated back to the direct drive. or speed reduction position or itcan be returned to the yneutral position, lw-ithout passing throughdirect drive or reducing position, by

- `merely rotating it .another 60 in the counterclockwise direction.

f If, while the valve 1 isin the neutral position shown in Figs. 17a-nd18, the respective control gears 4 and 4' are forced completely intomesh with the gear 3, and the pistons 8l are forced forward to utilizethe timing gears 5, 5 and 6 as pumping gea-rs, and thenthe valve l isrotated 60 in a clockwisedirection, the power output shaft 2| Vwill bedriven in a Vreverse direction relative to the power input shaft 8.

The valve l, under kthese conditions, is in the verse the direction ofrotation of the shafts I, is I three times the capacity of the firstgear set l, 2 `and 2 which tends to drive it forward. The

Vnet result is that the clockwise torque offsets the counterclockwisetorque and exceeds it bytwo times and drives the shaft 2l in reverse ata two to one reduction. This is illustrated bythe speed ratio equationas follows: k

+Cs '4 30s-F08: R21 Cs CS This reverse ratio can be increased withinfinite variation to a theoretically infinite voverdrive by graduallydecreasing the capacity of the controlling gear set 3, 4, 4 and timinggear set 5, 6 and 5', until it equals that of the controlled gears l, 2and v2. It will be noted that the same control pressure which 4causes areduction of gear ratio in forward drive, will cause an increase ofngearratio in reverse drive.

This transmission can be driven from the shaft :of the shaft 8.-

ldesired speed'or torque characteristics.

phere through ra small auxiliary reservoir, not shown), by some functionof the speed of rotation e When this centrifugal pressure is tapped atthe outlet connection 9|, it can be used to supply pressure through theconnection 42 for operating the valve-controlling gear .motor 39 and 48,Fig. '6,'there'by causing rotation of the A'control valve l from neutralposition to either k'forwardzor reverse drive, and making clutchingspeed afunction of the speed of the driving or power input shaft. Suchpressure may also be utilized to maintain` a positive pressure on thelow pressure side kof the pumping gears to preventy cavitation. Shouldthe speed of rrotation of the shaft 8 be a-factor in the desiredcontrol, it

may bevutilized to regulate the control pressures which, through`connections 93,93 and 92, 92', position the gears 4 `and 4.

The impeller I5 can be weighted yat its periphery to form a flywheel onthe shaft 8. Further, it can; be toothed tov mesh with a vstarting gearfor starting an internal combustion engine which might be coupled to theshaft'8. y v

. The difference in pressure betweenthe A ports and the B ports is alinear function of the torque applied to the shaft 8.' These twopressures may be tapped from the C :and D chambers at points T6 and` le.Through a suitable .rectifying valve (not shown) to allow for a reversalof pressures when theA torque is reversed, the low pressure side ofinput torque the difference in these two pressures maybe utilized toregulate the control pressure, if input torque is a factor in thedesired ratio control.

Hydraulic ratio control of this transmission' may-:be governed manuallythrougha throttle valve or may be completely automatic to give anyAutomatic control may be governed by any external factor or, withoutexternal influence, may mainmovable gear units of the variable capacitygear set3, `4-and 4`l against "hydraulic pressure of the vcontrol fluid:The end thrust on these axially mission ratio.v For this purpose, theoutlets T6 and 79 in the transmission housing provide any ideal sourceof fluid pressure differential for vuse in the ratio control. Thispressure differential is essentially equal to the. pressure differentialacross the ports of the variable capacity'gears,

which causes the end thrust on the axially movable gear unit. With thisas a starting pressure, control may be accomplished through a ratiocontrol valve which is adjustable to provide control iiuid at any setfraction of this pressure. Such control fluid will oppose the end thrustof the movable gear units with a pressure which iiuctuates to offsetfluctuations in this end thrust caused by variations in torque, and themeshing relationship of the variable mesh gears, and thus thetransmission ratio, will be dependent only upon the setting of the ratiocontrol valve.

vBriefly, automatic control of the transmission may be accomplished byusing any desired influence to regulate such a valve as just described.The control mentioned earlier for automotive use would be an example ofsuch an automatic control. The purpose of that control would be tomaintain a relationship between the speed and torque of the input shaft8 to correspond with the performance characteristics of the enginecoupled to it so that the engine would always operate at the mostadvantageous speed and torque to develop any desired power. One way ofaccomplishing this is to utilize both the pressure difference betweenthe outlets 90 and 9| in the transmission housing, which varies with thespeed of rotation of the shaft B, and the -pressure difference betweenthe outlets 16 and 19, which varies with the torque on the shaft 8, toregulate the ratio control valve.

In operation under this control, any variation which tends to cause thetorque on the shaft 8 to deviate from the relationship between torqueand speed designed into the ratio control valve operating means wouldchange the setting of this valve and thus change the transmission ratio.For example, if the transmission were operating at a small reductionratio with the gear 4 partially in mesh with the gear 3 and the loadtorque on the shaft 2| increased, the torque on the shaft 8 would beginto increase correspondingly. However this would cause an increase inpressure differential between the outlets 16 and 19 which would upsetthe balance in the ratio Ycontrol valve operating means, change thesetting of the ratio control valve, introduce additional iiuid into thechamber Q through the opening 93, and force the gear 4 farther intomesh. This would increase the reduction ratio'allowing the shaft 8 tomaintain its original torque and speed while the additional torque onthe shaft 2l would be obtained entirely through a sacrifice of speed atthat shaft.

If, under similar conditions, additional fuel were supplied to theengine driving the shaft 8, the additional power it would develop wouldfirst be evidenced by a slight increase in torque on the shaft 8. Thiswould increase the pressure differential across the outlets 16 and 19throwing the ratio control valve operating means out of balance andincreasing the reduction ratio of the transmission in the same manner asbefore. This would allow the shaft 8 to speed up increasing the pressuredifferential across the outlets 90 and 9|. This variation in speed andtorque would progress rapidly until a new balance of pressures wereattained in the ratio control valve operating means at which time theengine would again be operating most satisfactorily to develop theincreased power, The transmission ratio at which this condition would bereached would depend on the nature of the loading on the shaft 2l. Inother words, it would depend upon '20 whether lthe increased power wereabsorbed through increased speed or increased torque. This exampledemonstrates the flexibility with which the engine could operate despitea relative inexibility of loading.

In progressively increasing the reduction ratio, the gear 4' and thetiming gears 5, 6 and i6 would be brought into action as describedpreviously.

A decrease in torque would cause the reverse action to that describedfor increasing the torque. The gear 4 would be allowed to back fartherout of mesh by a reduction of iiuid pressure in the Q chamber and thereduction ratio would'decrease. If balance were not attained in theratio control valve operating means by the time the transmission was indirect drive, the ratio control means would supply fluid to the gearmotor 39-40 through the openings 42 and 43 to cause this motor to rotatethe valve l to overdrive position. Control fiuid would then beintroduced into the chamber P to check the tendency for the gear 4 tomove into greater mesh with the gear 3, as outlined in the discussion ofoverdrive ratios. K

With the addition of a single multiple port valve into the controls forthis transmission, it is possible to change instantly from automatic,infinitely variable control to any one of ve set speed ratios in a typeof operation which uses infinite variation only in changing betweenthese steps. The five positions which are attained by directintroduction of pumping pressure to give these speeds are: (1) allcontrol gears out of action (direct drive); (2) control gear 4 in mesh(7:4 reduction) (3) gears 6 and 6 pumping (5:2 reduction) (4) gears 6and 6' pumping and gear 4 in mesh (13:4 reduction); and gears 6 and 6pumping and gears 4 and 4 in mesh (4:1 reduction).

The embodiment of the invention illustrated in Fig. 19 simplifies theconstruction and control of the transmission considerably; however, italso decreases the range of speed variation which can be obtained with agiven size unit.

All parts in Fig. 19 are numbered the same as corresponding parts inFig. 1 with a dash and the numeral one added. The portions of thetransmission not shown in Fig. 19, that is, all parts forward of theplate 56-l, are the same as illustrated in Fig. 1 except that the F, F',G, and G ports terminate at the rear of section 4B of the housing and donot enter section 54.

The timing gears 5-I, B-I, and 6-| are not arranged here for use aspumping gears, and all of the ports, pistons, chambers and valvesillustrated in Figs. 11, l2, 13 and 14 which control the operation ofthe gears 5, 6 and 6' are eliminated. The gears 5-I, B-l, and 6-| arenarrower around their periphery, and have central hubs at their rearfaces, therebyv providing passage for free flow of fluid adjacent thegear teeth.

With this construction hydraulic control is accomplished in much thesame manner as described for the first construction, except that notiming gear control is necessary.

The embodiment illustrated in Fig. 20 constitutes a furthersimplification of the transmission. The plate 56 and section 58 of thehousing and the splined shafts 55 are all eliminated by attaching thetiming gears directly to the variable capacity gears. This constructionis particularly well suited to manual control. Such a control isillustrated.

In Fig. 20, parts which are identical with or modifications of parts ofthe first embodiment are designated by thesame numbenwith a dash and thenumeral 2 added. Additional parts are designated by numbers startingwith 100.

The gear 5--2 of the timing set is formed similarly to the gear `E-l inthe construction just described, so as to allow free ilow of fluid pastits teeth. 'Ihe gears 1|-2 and 62 are attached to the rear of the gears4-2 and 4'-2 by the screws and dowel pins |.0|, which also secure thespacer discs 53-2 and 53-2 in place.

The units made up of the gear 4 2, the spacer disc 53-2, the timing gear6--2 and their primed counterparts are adapted to rotate on therespective hollow shafts |02 and |02. The latter are xed againstrotation by the keys |03 and |03', which lock them'to the pistons lll- 2and 14T-2,v respectively. Locked nuts |04 and I 04 secure the shafts tothe pistons. Flanged heads |05 and |05 of shafts |02 and |02 hold therotating planet gear units against the rear of the pistons 41-2 and 4'|2with the proper running clearance.

The bores of hollow shafts |02 and |02! are decreased in diameter andthreaded for a short distance from the flanged ends, to receive threadedshafts |56 and |06. 4Circular flanges |01 and |01 on the shafts |05 and|06 are secured in ther rear cover plate 60-2 between sets of washers|08 and |08 by'means of cover plates |09 and |09', Vwhich are held inplace by screws ||0 and I0. The flanges |01, |01k serve not only toprevent axial motion of the shafts 06, |06', but also as seal rings toprevent fluid leakage along the shafts. At the external ends of theshafts |05 and |06' knurled knobs I|| and are at- :3.

the hydraulic control ports leading into the chamu' bers P, P', Q and Qare eliminated for manual control, it is necessary to provide anotherfluid connection between the P-2 and Q-2 chambers. This is done throughthe hollow shafts |02 and |02', and passages |2 through shafts |06 and05'.

This transmission has the same range of speed variation for a given gearsize as that illustrated in Fig. 19. completely out of mesh may,however, be considered a disadvantage in some instances, since thislimits the type of teeth which the gears 4-2.and 4-2 may have.

It is noted that any of the foregoing forms of the invention may bearranged for Aeither manual or hydraulic control of the clutch orcontrol valve l, ofthe variable capacity gears, and of the auxiliaryvalve for the timing gears where such is provided. The alterationsnecessary to adapt the transmission from one type of control to theother are not considered to involve more than ordinary mechanical skill,and are not described here. However, hydraulic control of the embodimentillustrated in Fig. must take into account the fact that there iscommunication between the Q-E and Q-2 chambers Thus it is necessaryeither to allow the two gears 4-2 and d-2 both to move into mesh at oncewhen control fluid is introduced into the Q-2 chambers, or to alter thecontrol so as to introduce high pressure fluid into the P-2 chamberwhile the control fluid in the Q-Z and Q-2 chambers is forcing the gear4-2 into mesh. In the latter instance the gear fik-2 is brought intomesh by reducing the iluid pres sure in the chamber P-2.

Whereas the invention has been here illus-A trated and described withrespect to severallp'referred specific forms thereof, it should beunder-,

stood that various kchanges may be made therein and various other formsmay be constructed by those skilled in the art, on the basis of theteachings hereof, without departing from the generic scope of theinvention as dened by the following claims.

Having fuuy described this inw/entier., what is at varying relativespeeds; gear-type, variable The fact that the timing gears movedisplacement, iiuid motive means coupling one of said power shaftsl tosaid housing for action either as a fluid motor or a fluid pump as thecase may be; a second fixed displacement fluid motive means coupling thesaid one Apower shaft to said housing; means interconnecting said secondfixed displacement fluid motive means with said variable displacementrluid motive means as a timer for the latter; fluid circulatory system`operatively interconnecting the first fixed displacement fluid motivemeans, the said variable displacement fluid motive means', and the saidsecond fixed displacement fluid motive means; principal Valve meanscontrolling flow of fluid through said circulatory system; auxiliaryvalve means disposed in said circulatory system between said variabledisplacement uid motive means and said second fixedl displacement fluid'motive means, for bringing said second iixeddisplacement fluidmotivemeans into operation in the system as a fluidmotor or fluid pump, as thecase may be; and means for varying the displacement of said variabledisplacement fluid motive means during operation of said transmission.

2. An infinitely variable power transmission, comprising a stationaryhousing; twol independent power shafts rotatably mounted in saidhousing; fixed displacement fluidmotive means coupling said power'shaftstogether for the transculatory system operatively'interconnecting saidfixed displacement fluid motive means, said variable-mesh gears, andsaid constant-mesh gears;

principal valve means controlling flow of iiuid f through saidcirculatory system; auxiliary Valve means disposed in said circulatorysystem between said variable-mesh gears and said constant-mesh gears,for bringing the constantmesh gears into the system as a duid motivemeans; means for varying the meshing relationship of said Variable-meshgears; and means for shrouding those portions of said variablemesh gearswhich are not intermeshed, against pressure iiuid from said circulatorysystem.

An infinitely variable power transmission in accordance with claim 2,wherein the set of variable-mesh gears comprises a gear mounted -onthesaid one power shaft, and one or more gears movable axially into greateror lesser meshing engagement with the said mounted gear;

wherein there is provided fluid-sealing means, including a pistonextending from each of said movable gears, said movable gears beingaxially fixed but rotatable with respect to the respective pistons;wherein there are formed, within said housing, cylinders disposedsubstantially parallel to said one power shaft, said movable gears andpiston extensions thereof being tted into the respective cylinders forlongitudinal movement; wherein said constant-mesh gears comprise aprimary timing gear mounted on said one power shaft, andone or moresecondary timing gears maintained in constant mesh with said primarytiming gear, and said secondary timing gears being in axial alignmentwith the respective movable gears of the said variable set, and beingmounted in common therewith on respective longitudinal shafts arrangedto transmit power between said secondary timing gears and said movablegears; wherein all of the said gears are helically toothed, the teeth ofthe said variable-mesh gears being formed to provide lines of sealobstructing flow of fluid axially between the meshing teeth; whereinthere is further provided a system of helical splines by means of whichall said gears are splined to their respective shafts, said helicalsplines having the gears movable axially into greater or lesser meshingengagement with the said mounted gear; wherein there is providedfluid-sealing means, including a piston extending from each of saidmovable gears, said movable gears being axially fixed but rotatable withrespect to the respective pistons; wherein there are formed, within saidhousing, cylinders disposed substantially parallel to said one powershaft, said movable gears and piston extensions thereof being fittedinto the respective cylinders for longitudinal I movement; wherein saidconstant-mesh gears comprise a primary timing gear mounted on said onepower shaft, and one or more secondary timing gears in alignment withthe respective movable gears of said variable-mesh set, a collar locatedbetween each secondary timing gear and the respective movable gear, saidcollar, secondary timing gear, and movable gear being fixed relativelyto one another, said collar constituting a part of said sealing means;and wherein the means for varying the said meshing engagement comprisesmanually adjustable members connected to the respective movable gearcombinations and accessible exteriorly of the transmission for movingsuch movable gear combinations backwardly or forwardly in the saidcylinders.

5. An innitely variable power transmission in accordance with claim 2,wherein the set of variable mesh gears comprises a gear mounted on thesaid one power shaft, and one or more gears movable axially into greateror lesser meshing engagement with the said mounted gear; wherein thereis provided fluid-sealing means,

.including a piston extending from each of said movable gears, saidmovable gears being axially xed but rotatable with respect to therespective pistons; wherein there are formed, within said housing,cylinders disposed substantially parallel to said one power shaft, saidmovable gears and piston extensions thereof being fitted into therespective cylinders for longitudinal movement; wherein thefluid-circulatory system is formed within said housing and includesports opening into the said mounted gear along the width of its toothedface, the said piston members being provided with wing extensions forvariably closing said ports in accordance with the extent of non-meshingengagement of the said movable gears with said mounted gear; and whereinthe means for varying the said meshing engagement comprises fluidsupplyconnections leading into opposite end portions of said cylinders.

6. An infinitely variable power transmission in accordance with claim 2,wherein the set of variable-mesh gears comprises a gear mounted on thesaid one power shaft, and one or more gears movable axially into greateror lesser meshing engagement with the said mounted gear; wherein thereis provided fluid-sealing means, including a piston extending from eachof said movable gears, said movable gears being axially fixed butrotatable with respect to the respective pistons; wherein there areformed, within said housing, cylinders disposed substantially parallelto said one power shaft, said movable gears and piston extensionsthereof being fitted into the respective cylinders for longitudinalmovement; wherein the fluid-circulatory system is formed within saidhousing and includes ports opening into the said mounted gear along thewidth of its toothed face, the said piston members being provided withwing extensions for variably closing said ports in accordance with theextent of non-meshing engagement of the said movable gears with saidmounted gear; wherein the principal valve means comprises a portedrotary valve member and a housing cooperatively ported, the respectiveports being so arranged as to provide, at one setting of the valve, forlocalized fluid circulations within the constant mesh gear set and thevariable mesh gear set, but no circulation between the two sets; andwherein the means for varying the said meshing-engagement comprisesfluid-supply connections leading into opposite end portions of saidcylinders.

7. An infinitely variable power transmission in accordance with claim 2,wherein the set ef variable-mesh gears comprises a gear mounted on thesaid one power shaft, and one or more gears movable axially into greateror lesser meshing engagement with the said mounted gear; wherein thereis provided fluid-sealing means, including a piston extending from eachof said movable gears, said movable gears being axially fixed butrotatable with respect to the respective pistons; wherein there areformed within said housing, cylinders disposed substantially parallel tosaid one power shaft, said movable gears and piston extensions thereofbeing tted into the respective cylinders for longitudinal movement;wherein the fluid-circulatory system is formed within said housing andincludes ports opening into the said mounted gear along the width of itstoothed face, the said piston members being provided with wingextensions for variably closing said ports in accordance with the extentof non-meshing engagement of the said movable gears with said mountedgear; wherein the prin-

